Xenomai 2.6.5 on Ubuntu 14.04/16.04

Download Xenomai 2.6.5

wget http://xenomai.org/downloads/xenomai/stable/xenomai-2.6.5.tar.bz2
tar xfvj xenomai-2.6.5.tar.bz2

Download Linux kernel 3.18.20

wget https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.18.20.tar.gz
tar xfv linux-3.18.20.tar.gz


We chose 3.18.20 because it is the latest kernel compatible with xenomai 2.6.5.


Prevent a bug in make-kpkg in 14.04

From https://bugs.launchpad.net/ubuntu/+source/kernel-package/+bug/1308183 :

cd linux-3.18.20
# Paste that in the terminal
cat <<EOF > arch/x86/boot/install.sh
cp -a -- "\$2" "\$4/vmlinuz-\$1"

Prepare the kernel

sudo apt install kernel-package

Patch the Linux kernel with Xenomai ipipe patch

cd linux-3.18.20

Press Enter to use the default options.

Configure the kernel

Now it’s time to configure :

Gui version :

make xconfig

Or without gui :

sudo apt install libncurses5-dev
make menuconfig

Some guidelines to configure the linux kernel:

Recommended options:

* General setup
  --> Local version - append to kernel release: -xenomai-2.6.5
  --> Timers subsystem
      --> High Resolution Timer Support (Enable)
* Real-time sub-system
  --> Xenomai (Enable)
  --> Nucleus (Enable)
      --> Pervasive real-time support in user-space (Enable)
* Power management and ACPI options
  --> Run-time PM core functionality (Disable)
  --> ACPI (Advanced Configuration and Power Interface) Support
      --> Processor (Disable)
  --> CPU Frequency scaling
      --> CPU Frequency scaling (Disable)
  --> CPU idle
      --> CPU idle PM support (Disable)
* Pocessor type and features
  --> Processor family
      --> Core 2/newer Xeon (if \"cat /proc/cpuinfo | grep family\" returns 6, set as Generic otherwise)
* Power management and ACPI options
  --> Memory power savings
      --> Intel chipset idle memory power saving driver (Disable)


For OROCOS, we need to increase the amount of ressources available for Xenomai tasks, otherwise we might hit the limits quickly as we add multiples components/ports etc. http://www.orocos.org/forum/orocos/orocos-users/orocos-limits-under-xenomai

* Real-time sub-system
  --> Number of registry slots
      --> 4096
  --> Size of the system heap
      --> 2048 Kb
  --> Size of the private stack pool
      --> 1024 Kb
  --> Size of private semaphores heap
      --> 48 Kb
  --> Size of global semaphores heap
      --> 48 Kb

Save the config and close the gui.

Compile the kernel (make debians)

Now it’s time to compile.

CONCURRENCY_LEVEL=$(nproc) make-kpkg --rootcmd fakeroot --initrd kernel_image kernel_headers

Take a coffee and come back in 20min.

Compile faster with distcc

If you have distcc servers setup and a fast network, you can speed up drastically the building speed.

MAKEFLAGS="CC=distcc" BUILD_TIME="/usr/bin/time" CONCURRENCY_LEVEL=$(distcc -j) make-kpkg --rootcmd fakeroot --initrd kernel_image kernel_headers

Install the kernel

cd ..
sudo dpkg -i linux-headers-3.18.20-xenomai-2.6.5_3.18.20-xenomai-2.6.5-10.00.Custom_amd64.deb linux-image-3.18.20-xenomai-2.6.5_3.18.20-xenomai-2.6.5-10.00.Custom_amd64.deb

Allow non-root users

sudo addgroup xenomai --gid 1234
sudo addgroup root xenomai
sudo usermod -a -G xenomai $USER


If the addgroup command fails (ex: GID xenomai is already in use), change it to a different random value, and report it in the next section.

Configure GRUB

Edit the grub config :

sudo nano /etc/default/grub
GRUB_DEFAULT="Advanced options for Ubuntu>Ubuntu, with Linux 3.18.20-xenomai-2.6.5"
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash xeno_nucleus.xenomai_gid=1234"


Please note the xenomai group (here 1234) should match what you set above (allow non-root users).


noapic option might be added if the screen goes black at startup and you can’t boot.

If you have an Intel HD Graphics integrated GPU (any type) :

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_rc6=0 i915.powersave=0 noapic xeno_nucleus.xenomai_gid=1234 xenomai.allowed_group=1234"
# This removes powersavings from the graphics, that creates disturbing interruptions.

If you have an Intel Skylake (2015 processors), you need to add nosmap to fix the latency hang (https://xenomai.org/pipermail/xenomai/2016-October/036787.html) :

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_rc6=0 i915.powersave=0 xeno_nucleus.xenomai_gid=1234 nosmap"

Update GRUB and reboot

sudo update-grub
sudo reboot

Install Xenomai libraries

cd xenomai-2.6.5/
make -j$(nproc)
sudo make install

Update your bashrc

echo '
#### Xenomai
export XENOMAI_ROOT_DIR=/usr/xenomai
export XENOMAI_PATH=/usr/xenomai
export OROCOS_TARGET=xenomai
' >> ~/.bashrc

Test your installation

xeno latency

This loop will allow you to monitor a xenomai latency. Here’s the output for a i7 4Ghz :

== Sampling period: 100 us
== Test mode: periodic user-mode task
== All results in microseconds
warming up...
RTT|  00:00:01  (periodic user-mode task, 100 us period, priority 99)
RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat best|--lat worst
RTD|      0.174|      0.464|      1.780|       0|     0|      0.174|      1.780
RTD|      0.088|      0.464|      1.357|       0|     0|      0.088|      1.780
RTD|      0.336|      0.464|      1.822|       0|     0|      0.088|      1.822
RTD|      0.342|      0.464|      1.360|       0|     0|      0.088|      1.822
RTD|      0.327|      0.462|      2.297|       0|     0|      0.088|      2.297
RTD|      0.347|      0.463|      1.313|       0|     0|      0.088|      2.297
RTD|      0.314|      0.464|      1.465|       0|     0|      0.088|      2.297
RTD|      0.190|      0.464|      1.311|       0|     0|      0.088|      2.297


To get pertinent results, you need to stress your system while running the latency test. The latency has to be stable even if the system is under load.

sudo apt install stress
# Using stress
stress -v -c 8 -i 10 -d 8

Negative latency issues

You need to be in root sudo -s, then you can set values to the latency calibration variable in nanoseconds:

$ echo 0 > /proc/xenomai/latency
# Now run the latency test

# If the minimum latency value is positive,
# then get the lowest value from the latency test (ex: 0.088 us)
# and write it to the calibration file ( here you have to write 88 ns) :
$ echo my_super_value_in_ns > /proc/xenomai/latency

Source : https://xenomai.org/pipermail/xenomai/2007-May/009063.html